Thermometer-scale



(No Model.)

P. BRANDT. THERMOMETER SCALE. No. 478,984. Patehted July 19, 1892.

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UNITED STATES PATENT OFFICE.

FRANZ BRANDT, OF PHILADELPHIA, PENNSYLVANIA.

TH ERMOM ETER-SCALE.

SPECIFICATION forming part of Letters Patent No. 478,984, dated July 19,1892.

Application filed April 13, 1892. Serial No. 428,940. (No model.)

To all whom, it may concern:

Be it known that I, FRANZ BRANDT, a citizen of the United States,residing at the city of Philadelphia, in the county of Philadelphia andState of Pennsylvania, have invented certain new and ImprovedThermometer-Scales,

of which the following is a specification.

My invention relates in general to thermometers, and more particularlyto the construction and arrangement of the back plate or mounting withwhich the tube containing the mercurial or other sensitive fluid columnis usually connected.

Hitherto it has been customary to provide the tube containing themercurial or other sensitive column with a complemental scale for notingor registering the movements of the fluid column. In some cases thisscale has been engraved upon the tube or upon the back plate or support.However, such a scale is not clearly discernable. This objection has inpart been overcome by painting the scales either with or withoutpreviously engraving them. However, such painting is expensive and isobliterated in a short time by the action of heat, moisture, and acids,to which most, if not all, the thermometers are to a greater or lessextent in use exposed.

The principal object of my present invention is to dispense with theemployment of paint and other like pigments and to produce aninexpensive, attractive, and durable thermometer-scale that iscontrastedin color with its background and is absolutely impervious to thedestructive influences to which thermometers are generally exposed.

My invention consists of a composite thermometer-scale comprisingsuperposed and united plates, sheets, or layers suitably contrasted incolor and having portions of the exterior sheet, plate, or layer etchedcompletely away to expose portions of an underlying sheet, plate, orlayer, whereby the figures and background of the scale are stronglycontrasted; and my invention further consists of the improvementshereinafter described and claimed.

panying drawings, forming part hereof, and in which Figure 1 is a frontelevation of a thermometer-scale embodying features of my invention andshowing at the top thereof the gradua tions and accessories of a scaleetched through a dark exterior plate,.sheet, or'layer and appearing upona light interior plate, sheet, or layer, and also showing at the bottomthereof the graduations and their accessories produced in dark color byetching out the background in the dark exterior plate, sheet, or layer,and thus causing the same to appear upon a light interior plate, sheet,or layer. Fig. 2 is a sectional view illustrating the process ofproducing a thermometer-scale embodying features of my invention. Fig. 3is a longitudinal central section of the upper portion of Fig. 1,showing the graduations and the accessories of the scale etched throughthe dark exterior plate, sheet, or layer and appearing on the lightinterior sheet, plate, or layer; and Fig. 4 is a similar View of thelower portion of Fig. 1, showing the background of the scale etchedthrough the dark exterior plate, sheet, or layer and appearing on thelight interior sheet, plate, or layer.

In the drawings, A is a composite thermometer scale comprising twosuperposed and united plates, layers, or sheets a and b, suitablycontrasted in color. In the present instance the sheeta is presumed tobe composed of red glass and the sheet Z) of ground, clear, ortransparent glass. However, any preferred materials or colors may beemployed. These sheets, layers, or platesa andb may be superposed andfirmly united together by heat and pressure or in any other preferredmanner.

0 are the graduations and accessories of the scale, and d is thebackground, and it is important that these two should be as stronglycontrasted as possible in order to facilitate the operation of readingthe thermometer. In my invention this result may be attained by etchingthe graduations and accessories 0 completely through the red glass a, sothat they appear in white or transparent glass 1), as shown at the upperportion of Fig. 1, or by etching the background d completely through thered glass at, so that it appears in white or transparent glass Z), asshown at the lower portion of Fig. 1. In either case the respectivecolors of the background and of the grad nations are both permanent andthe complete scale is exceedingly durable, because the coloredglassplates, sheets, or layers a and b are not in anywise affected by thedestructive influences to which thermometers are in practice exposed.

\Vhen clear glass is employed as a background of the scale, as shown inFig. 4, the rear face of the sheet, layer, or plate Z) is preferablyground or dulled, as at e, in order to make the backgroundopaque,wl1ereby the graduations and their accessories 0 are renderedmore distinct than would be the case if they appeared upon atransparentglass plate, sheet, or layer Z).

In order that the invention may be more fully understood, a briefdescription of a practically efiicient method of producing thehereinabove-described thermometer'scale will now be given.

The red plate, sheet, or layer a and the transparent plate, sheet, orlayer 1) are united by fusion and rolling or in any other preferredmanner to form the composite thermometer-scale A. One surface of thisscale is then coated with wax, asphalt, and oil or other acid-resistingmaterial f, and the graduations and their accessories 0 or thebackground (Z, according as the one or the other is required to appearin white in the finished article, are drawn upon the coated face of thescale A by the removal of corresponding portions of the wax or otheracid-resisting material, as shown at the left-hand portion of Fig. 2.The scale is then subjected to the action of fluohydric acid and camphoror other suitable materials that will attack glass and not the Wax orother acid-resisting material in the usual manner. Of course care shouldbe exercised to permit the acid to etch its way completely through theexposed portions of the plate, layer, or sheet a, so that the sheet,layer, or plate 6 is exposed to View, as is illustrated at theright-hand portion of Fig. The etched scale A is then suitably washed,and after being supplied with a thermometer bulb and tube (not shown) isready for use. If required, the rear face of the scale A may be groundby means of a sand-blast, or by exposure to the fumes of fluohydricacid, or in any other preferred manner.

It may be remarked that a scale embodying features of my invention maybe produced upon the glass tube of the thermometer or upon otherinstruments of precision, as barometers. Hence I do not limit myself tothe exact construction and arrangement hereinbefore explained, andillustrated in the drawings; for,

Having thus described the nature and objects of my invention, what Iclaim as new, and desire to secure by Letters Patent, is-

1. A panel for thermometers, composed of composite or flashed glass andhaving on its face an etched scale, substantially as and for thepurposes set forth.

2. A panel composed of composite or flashed glass and adapted for thereception of a thermometer tube and having on its back a ground-glasssurface and having on its face an etched scale, substantially as and forthe purposes set forth.

3. A panel composed of etched composite material, as flashed glass, forholding a thermometer tube and bulb, substantially as and for thepurposes set forth.

In witness whereof I have hereunto set my signature in the presence oftwo subscribing witnesses.

FRANZ BRANDT.

\Vitnesses:

THOMAS M. SMITH, RICHARD C. MAXWELL.

